1. Field of the Invention
The invention relates to a display device, specifically to a display device having a lighting device and a reflective liquid crystal display device.
2. Description of the Related Art
A liquid crystal display device (hereafter, referred to as a LCD) is thin and consumes low power in its characteristics, and has been broadly used as a monitor of a computer or a monitor of a mobile data terminal such as a cellular phone. There are a transmissive LCD, a reflective LCD, and a semi-transmissive LCD as the LCD. In the transmissive LCD, a transparent electrode is used as a pixel electrode for applying a voltage to a liquid crystal and a back light is set in the rear of the LCD, so that a bright display can be realized by controlling a transmission amount of light of this back light even in the dark. However, in an environment where external light is strong such as out of doors in the daytime, a contrast can not be obtained enough.
The reflective LCD uses external light such as sunlight or interior light as a light source, and reflects the external light entering the LCD by a reflective pixel electrode formed of a reflective layer formed on a substrate on a viewer side. The reflective LCD makes a display by controlling an amount of light released from a LCD panel in each of the pixels after the light enters a liquid crystal and is reflected by the reflective pixel electrode. Since this reflective LCD uses external light as a light source, there is a problem that the display can not be made in an environment of no external light.
The semi-transmissive LCD has both the transmissive function and the reflective function, and is applicable to both the bright and dark environments. However, since this semi-transmissive LCD has a transmissive region and a reflective region in a pixel, there is a problem of low display efficiency in each of the pixels.
For solving this, it has been suggested that a front light is provided in the reflective LCD to realize a display even in the dark environment. FIG. 13 is a view showing a display device with the reflective LCD and the front light of a conventional art. A transparent acrylic plate 110 is disposed, being opposed to a display surface of a reflective LCD 100. A plurality of grooves 111 shaped in inverted triangles is formed on a surface of this transparent acrylic plate 110, which is on the opposite side to the side opposed to the reflective LCD 100. Furthermore, a light source 112 is disposed on a side surface of the transparent acrylic plate 110. Light entering the transparent acrylic plate 10 from the light source 112 is refracted in a direction to the reflective LCD 100 by inclined surfaces of the grooves 111 shaped in inverted triangles, and enters the display surface of the reflective LCD 100.
The relating technology is described in the Japanese Patent Application Publication Nos. 2003-255375 and H5-325586.
However, the light entering the transparent acrylic plate 110 from the light source 112 is refracted in a direction to a viewer 113 on the opposite side to the reflective LCD 100 by a small amount as well as in the direction to the reflective LCD 100 by the inclined surfaces of the grooves 111 shaped in inverted triangles provided in the transparent acrylic plate 110. Therefore, the small amount of light leaks from the transparent acrylic plate 110 to reach eyes of the viewer 113, causing a problem of degrading the contrast of the LCD display.